Such a control system is known from German Pat. No. 1 605 260. In the case of this known control system, the electrical relay system can only be controlled after the second electrical control system has responded, i.e., the brake or release circuit can only be excited after shifting of the piston by a pressure difference between the preliminary control and main air line pressures. It follows that, in case of minor control operations at the servo valve which effect only a minor change in the pilot pressure that is not sufficient for the operation of the piston, the electrical relay system will not respond and the brake or release circuit is not excited. Therefore, the minor control operations can only be performed purely pneumatically and, thus, in case of fairly long trains with a correspondingly long delay. Apart from that, the known control system is designed in such a way that no counter-control can be effected by exciting the release circuit if pressure reductions occur in the main air line while the pilot pressure remains constant, so that emergency braking effected from the train can become smoothly and quickly effective. On the other hand, if pressure increases occur in the main air line, e.g., through temperature changes or vibrations, the known control system can respond and can effect undesirable and excessive counter-control by excitation of the brake circuit.